Electrophotographic process



l1g 9, 1965 R. M. SCHAFFERT 3,266,045

ELECTROPHOTOGRAPHIC PROCESS Original Filed Sept. 26, 1962 Flai HG2 4.6M f f xxxxx x o I H FIG. 5 l12 FIG.7

i2 INVENTOR,

` ROLAND NI. SCHAFFERT ATTORNEY' United States Patent O Y ELECTROPHOTOGRAPHIC PROCESS Roland Michael Schaffert, Saratoga, Calif., assignor to International Business Machines Corporation, New York, N .Y., a corporation of New York Continuation of application Ser. No. 226,376, Sept. 26, 1962. ,This applicationOct. 19, 1965, Ser. No. 505,127

16 Claims. (Cl. 346--1) This application is a continuation of the copending U.S. patent application Serial Number 226,376, filed on September 26, 1962, which application -isnow abandoned.

The invention relates to electrophotography, and it particularly pertains to processes for use with electrophotographic film structures which can be developed by heat and viewed with simple optics.

A technique for rendering electrostatic charge patterns visible in the form of Lichtenberg gures on certain dielectricfsurfaces by the application o-f heat is described in an article by A, M; Thomas in the British Journal of Applied Physics, volume 2,'April 1951, pages 98-109. As described in this article, electrostatic patterns become visible in the form of :small ridges, creases or pits in the otherwise smooth surface of the dielectric.

Another thermoplastic recording technique is described in an article by W. E. Glennfinthe Journal ofAppli'ed Physics, volume 30, No. 12, December 1959, pages 1870- 1873. As described in this article, the film structure consists of a sandwich comprising a high'melting base film, a`transparent conducting coating laid down on the b-ase film, and a low meltingfthermoplastic layer laid down on the conducting coating. The sandwich is` placed in a 'vacuum chamber in which an .electron gun is arranged. A charge Vpattern is laid down'on the upper surface 'ofthe thermoplastic film yby scanning the'electron beam: overl the surface. The film is thenfheated to the melting point of the thermoplastic permitting the electrostatic fo'rces between the charges on thefilmiand the conductive coating to depress thesurface'of the thermoplastic where the charges occur until these 'forces are'in equilibrium with the sur-face tension restoring forces. The film structure is then cooled belowlthe melting point of the thermoplastic and the deformations are retained in the solidified surface. Erasure is accomplished by heating-the film well above the melting point in the` absence of any c-harge'p-attern whereby surface .tension will then smooth out the deformations and the film is ready for reuse. According to this disclosure, the yfilm is usually heated' in the vacuum cham-ber for developing the'deformations by inducing current in the transparent conducting coating. A modified Schlieren optical system is necessary for viewing the heat developed images.

'A form of eidophor Vfor astronomical observation purposes is described by H. W. Babcock in the Journal of kthe Optical Society of America, volume 48, No. 7, July 1958, in which the variable optical element is ,a thin, uniform, flexible, solid film of low, but finite electrical conductivity. A reflecting coat of aluminum isplaced `on one side of the film and the other side is coated with a mosaic of isolated target elements. The film is mounted Within a cathode ray tube equipped with a transparent window instead of the usual screen with the aluminumized side of the thin film facing outward. The other side of .the film thenv receives a raster charge'deposited on the mosaic -by the electron gun of the cathode ray tube. The resulting electrostatic forces give rise to correspond- `ing deformation of the otherwise plane reflecting surface.

The necessity for producing electrostatic images on .the

Vfilm in Vacuum by the prior art method is, of course, a rconsiderable disadvantage;

Likewise,` the 'facts that only line images can be developed and that these must be ob- Patented August 9, 1966 served with the aid of `Schlieren optics represent disadvantages.

An object of the invention is an electrophotographic process in which electrostatic images canbe produced on film in air by known techniques and then developed lin air, obviating the requirement for a vacuum chamber and the necessity of inserting the film therein and removing it therefrom.

Another object of the invention is to be able to develop continuous-tone images as well as line images.

A further object of the invention is .to produce images which can be observed visibly without the aid of special optical systems. v l

Still another object of the invention is to produce a method applicable to direct photography, obviating the use of powders and powder handling devices and the attendant machine fouling problems.

A more specific object of the invention is to provide film structures for producing a photographic record in the form of electrostatic images by thermal development.

These objects are attained by a process wherein an electrostatic image is first established by known methods on a dielectric film structure .according to the invention. After producing an electrostatic image on the dielectric, such as for example with the aid of a photoconductive member, the film structure according to the invention bearingY a latent electrostatic image is heated for a sort time by known means `to a temperature above the melting point of one of the constituents of the film structure to develop the image which may be seen wit-h the naked eye and handled in simple optical systems.

Heat developing film structures according to the inventionfor producing visible images corresponding to electrostatic charge patterns established on the film generically comprise a sandwich of .a base layer, an outer heating to those areas corresponding to the electrostatic charge pattern. At least the outer layer or stratum has a melting point lower than that of the other layers. In some forms of the invention the outer and intermediate strata are not separated by any fine line of vdemarcation and, therefore, havethe same melting point. layer is conductive to an extent sufficient for the image transfer process and is preferably, but not necessarily, transparent. In some cases the base layer` may be stripped Vaway from the remainder of the film if such is self-supporting after it is developed. In such cases, the base layer may be a metal plate.

'Ihe film structures according to the invention take different forms for different applications. there is preferably, but not necessarily, a transparent base layer of suitable material on which there is -a conductive layer and an .outer layer of transparent dielectric material which has a melting pointlower than that of th other layers. l

A desired image established onto thesunface of -the dielectric mater-ital as an electrostatic charge pattern is made -visibleupon application orf heatas a roughened area lying in a smooth background.

Another film structure according to the invention'cornprises a stratum layer of low melting point resin film nor- The base I In one form' A further film structure according to the invention comprises upper and intermediate layers of wax or resin with a polycrystalline structure which is normally opaque rendering a diffused refraction of l-ight at the interfaces of the crystals. lThe lowered surface tension orf the melted layers subjected to the electric stress at the electrostatic charge image areas renders the crystals amorphous on the application of heat. The image th-en appears as a transparent area in an opaque background.

Another film structure according to the invention comprises a strata orf resin having a smooth surface beneath which is' more of the material containing minute capsules filled with dye-forming material. An intermediate layer contains a chemical which will react with the dye-forming material. Upon the application of heat above the melting point of the resin, a colored image is formed in the areas :where the electrostatic stress is sufcient to cause the capsules of dye-forming material to collapse, thus releasing the dye-forming material to react with the chem-ical.

Still another film structure according to the invention comprises a stratum of fusible resin containing embedded infin-sible particles cov-ered by another stratum of fusible resin only providing an optically smooth surface. The combination of heat with the electrostatic stress in the yimage areas compresses the resin below the upper portions of the infusible particles. This produces an image of roughened or grainy consistency on a smooth background.

A further film structure according to the invention comprises an outer continuous layer of one resinand a layer of compound reactive with each other to produce a color change and separated by a very th-in layer of fusible resin.

Upon the application of heat, the fusible resin flows sidefways because of the electrostatic stress in the image lines, allowing lthe one resin and the reactive compound to come into contact and produce a colored image visible to the eye.

Still another film structure according to the invent-ion comprises an upper continuous stratum orf thermoplastic resin and an intermediate stratum of the same thermoplastic resin having a di-spersion orf elongated dielectric or ferroelectric particles of random orientation. In the electrost-atically charged image areas, the heat melting therein twill permit the particles to align themselves with the electrostatic field, thus allow-ing the passage of light normally blocked by the rand-om oriented particles to form a photographic transparency.

In order that full advantage of the invention may be readily obtained in practice, preferred embodiments thereof, given byway of examples only, are described in detail hereinafter with reference to the accompanying drawing forming a part or the specification, and in which:

FIG. l'illlustrates the establishment of an electrostatic image charge pattern on a film structure according to the invention;

FIG. 2A illustrates the heating step in the development of an image according to the invention;

yFIG. 3 illustrates a film structure according to the invention comprisingbubbled filled resin;

FIG. 4 illustrates a film structure according to the invention comprising crystalline Wax or resin;

FIG. 5 shows another film structure according to the invention comprising dye-filled capsules for reaction with a dye-forming material;

FIG. 6 shows a further film structure according to the invention wherein a fusible resin film contains embedded infnsible particles;

FIG. 7 shows still another yfil-.rn structure accord-ing to the invention comprising two reactive materials separated by a thin layer of fusible resin; and

FIG. 8 illustrates a further lm structure accord-ing to the invention comprising a fusible resin containing a dispersion of elongated dielectric or fcrroelectric particles of random orientation.

FIG. 1 is an illustration of electrostatic image formation by one means on a film structure 10 according to the invention comprising a transparent base layer L2, a transparent conductive surface element 1.3, and a film 14 of melting point lower than that of the base layer. An example off the base layer 12 is polyethylene terephthalate and the conductive element l13 for such an example is a thin deposit of aluminum. Ilf desired, a known form of conductive glass m-ay be substituted for the combination. Examples of the lrn 14 are ester gum (iwith and Without pllasticizer), cumar resin, maleic anhydride resin, silicone varnish, petroleum wax and polyethylene. A charge pattern on a xerographic plate 1'6 comprising a metallic sul strate 1,8 and a selenium layer 19` is produced by conventional means. The image appear-ing on the selenium layer 1K9l is transferred to the film structure 10. Methods and apparatus for establishing electrostatic images on dielectric material are well known. There are also preferred processes of electrostatic image transfer described in the copending U.S. patent applications of Harold C. Medley and Roland M. Schaffert, Serial No. 127,725, filed on July 28, 1961, and of Roland M. Schaffert, Serial No. 159,892, filed on December 18, 1961, and now Patent No. 3,147,769. The establishment of the image on the xerograpbic plate 16 and the subsequent transfer to the film structure 10 in and of themselves form no part orf the invention as such operations are well known to those skilled in the art.

Development of the image on the film structure 10 is shown in FIG. 2 :wherein the exposed film structure 10 is subjected to heat from a suitable source, such as the cornbin-ation of an infra-red lamp 20 and a reflector 22 as shown. The film 14 is heated by the lamp 20 slightly above the melting point whereupon the surface tension and the stresses of the elestrostatic forces of the charge produces roughness of the surface as shown at line 15. There will be diffuse reflection in the image areas due to surface roughness and specular reflection in the background areas. Itf the film. is transparent, the surface distortion in the image areas will cause differential refractive effects, and when viewed by transmit-ted light,- the image areas will cast a shadow, giving the effect of a photographic transparency.

Thus, a photographic transparency has been developed Without resorting to powder and powder developing devices, and without the necessity o-f inserting parts into and moving them from vacuum chambers.

;F IG. 3 illustrates a film structure according t-o the invention which functions to produce a visible image in a manner somewhat different from the simple film structure shown in FIGS. 1 and 2. In FIG. 3 and the following figures, an enlarged cross-sectionof the film structure is shown. At the left is the structure before developing by heating and fixing by cool-ing and at the right is an example of a line or small area after processing according to the invention. A film structure 30 according to the invention comprises .a b'ase layer 12 and a layer 32 having an upper stratum 34 with a smooth obverse surface 38 and an intermediate stratum 36 filled with gas bubbles as shown. 'Ihe obverse surface 318 is smooth and continuous in contrast to the spongy nature of the intermediate stratum 36. Otherwise, the layer 32 is homogeneous and there is no finite line of demarcation between the strata 34 and 36. 'Ilhe Afilm 32 may be formed by exposing a vesicular film uniformly overall to ultra-violet light creating bubbles which render the film white and translucent. An example of such film -is polyvinyli-dene chloride containing a diazo compound and known better by the trademark Kalfax 'Ilhe base layer 12 is a transparentmaterial which may be conductive or have a conductive fil-m laid thereon. For example, the base layer 12 is polyethylene terphthalate film manufactured and sold under the trademark Myl-ar and the conductive surface necessary fpr the establishment of the charge according to the desired image is a transparent coating of aluminum. Alternatively, other transparent conductive coatings, or a conducative glass material may be used. Where transparency is not required, a metal base layer is practical. Some of the iilm structures according to the invention are selfsupport-ing and may be removed from the base layer 12 after development. In such cases a metal base layer is quite practical. Upon ysubject-ing the exposed lm t-o the charge pattern and transferring the charge thereto and thereafter subjecting the exposed film to heat, the surface tension and the electrostatic stress coact to collapse the bubbles in the areas corresponding to the charge rendering the film 32 clear and transparent at these areas, Whether t-hey be the sm'all areas of a line image or the larger areas rcomprises a base layer 12, a conductive coating or layer 13 and another layer having two strata: a foam or sponge stratum 36 of chemically blown polyvinyl chloride plastisol or IFreon blow polyurethane foam topped :with a smooth stratum 34 of the same material. In this embodiment there is actually no ne ydemarcation between strata, the only point made is that it is preferable, but no really necessa-ry, that the obverse surface 38 be smooth and cont-inuous as contrasted Wit-h the spongy surface that would appear otherwise. An example of alternative film structure 30 according to the arrangement shown in FIG. 3 is made of a Mylar base film 12 about 5.0 mils thick with an aluminum layer 13 deposited thereon, atop which is a layer of foam resin. Y

Another ilm structure40` according to the invention is shown in FIG. 4 comprising a base llayer 12 and a ilm l'ayer 42 consisting of two strata with one stratuml 44 comprising crystal-line wax or resin crystals of random structure and the other stratum 46 comprising crystals of the same material, but of structure forming a smooth obverse surface 48. Like the previous embodiment, there is no ine line of demarcation between strata. Ag-ain, the substrate `12 may be transparent or opaque; optionally black or of another color, as previously describe-d. When eX- posed to an electrostatic charge and thereafter heated, the crystals i-n the image area fuse tothe amorphous state permitting light to be transmitted through the image area which is of a light transmitting characteristic contrast-ing with that of the crystalline wax or resin. An example of a material suitable for this embodiment is crystalline polyethylene.

FIG, 5 depicts a 'further film structure 56 according to the invention comprising a base or reverse layer 12, an upper or obverse layer 5-2 comprising resin fil-m containing encapsulated dye former and an intermediate layer 56 containing a chemical reactive with the dye former. The obverse surface 58 of the encapsulated resin lrn 52 is smooth. When an electrostatic image is formed on the film and it is heated, the electrostatiestress and surface tension in the image areas coact to collapse the dye former capsules causing a reaction with the reactive chemical in the intermediate layer 56 reproduce an area of contrasting optical characteristics visible to the naked eye.

The encapsulating of dye formers and the resulting formation of la marking of optically contrasting character- -istic upon rupture by pressure of a stylus or typebar are Well known in the art. These form no part of the invention in and of themselves, the invention being concerned Vwith the application of heat and electrostatic pressure for Making the Same; Seri-al No. 11,341, of Z. Reyes, filed February 26, 1960, for Process of Making Microcapsules; Serial No. 39,150, of H. Huff et al., tiled June 27, 1960, and now abandoned for Process of Making Microcapsules;v and Serial No. 66,688, of Z. Reyes, filed Nove ber 2, 1960, for Preparation of Polyvinyl Alcohol Microcapsules, are suggested for thedetails of the arrangements, bearing in mind that the materials and methods set forth. therein should be selected with an eye to the reactions to heat and electrostatic pressure for the practice of the instant invention.

A further lm structure 60 acco-rding to the invention is shown in FIG. 6; In this embodiment of the invention a layer 62 comprised of fusible resin film is `laid upon base layer 12 and Ia conductive film 1'3. 'Ehe layer 62 has fa stratum 64 containing embedded infusible particles 65. All o-f the particles 65 are below an obverse stratum 66 so that the obverse surface 68 is optically smooth and somewhat removed from the particles 65. The fusible resin melts when exposed to heat and the electrostatic stress plus the reduction in surface tension pulls the surface 68 down belotw the tops of the particles 6'5 in the charged areas as shown at the right forming a roughened surface similar to that shown at 15 in FIG. 2.

The particles of infusible material can be powdered or ground glass, magnesium acetate, magnesium sulphate, and the like. The index of refraction should be comparable for both the resin and the particles. For example, light flint glass, the index of refraction of which lies in the range of 1.605-1.572, can be used with polystyrene which has an index of'refraction (LR.) of 1.59. Polyethylene, -I.R. 1.51 will go well with ordinary crown glass, I.R. 153241511, as will acrylate, LR. 1.49-1.51. Other combinations are suggested, for example, polyvinyl acetate, LR. 1.46-1.5 and magnesium acetate, LR. 1.49 which should not be too finely ground. Polyvinyl acetate and magnesium sulphate in one of its forms may be used. Thelatter in one form, with 5 molecules of Water of hydration, has an LR. of 1495-1514. In its common form, with 4 molecules of water of hydration, it has an LR. of 1508-1522 and rose colored, which fact may discourage its use somewhat. Acrylate and albite glass, LR. 1.489 are also suggested.

The particles 65 alternatively are reactive with a chemical to change color. This chemical would be swabbed over the surface after development by heating and xing by cooling to color only the exposed particles to provide the desired contrast.

FIG. 7 illustrates a still further embodiment of the invention comprising a film stru-cture 70 having a base layer 12, a layer 72 of one resin, for example, vinyl resin, and a layer 74 of a zinc compound, for example, zinc oxide, separated by 'a very thin layer 76 of fusible resin, which preferably is White or transparent. and heat causes the very thin layer 76 of fusible resin to melt and allows the vinyl resin to contact the zinc compound leaving an area of contrasting optical characteristics in the image areas. For the example given, of Zinc oxide and vinyl resin, the exposed and ydeveloped areas will be black providing a very effective image visible to the naked eye. For this embodiment of theinvention, the reaction between dimethyl glyoxime and nickelous chloride is also suggested.

A different film structure Sti according to the invention is shown in FIG. 8. This film structure 80 comprises a lbase layer 12, a conductive iilm 13, and a layer of fusible resin 82 having an upper strata 84 and an intermediate strata 86 of fusible resin containing a dispersion of elongated dielectric crystals. Here, electrostatic stress plus heat permits the orientation of the crystals inthe direction of the electrostatic field, thereby providing an optical characteristic of contrasting nature in the image area to that in the background. An example ofcrystals for this embodiment is calcium citrate, which is in the form of elongated white needles. It is not important Electrostatic stressl lto match the indi-ces of refraction in this embodiment.

The randomly oriented crystals in the resin, say polyethylene, render the film structure fairly opaque and more light will be transmitted where the crystals are aligned, though not nearly as much contrast will be afforded here as with some of the other embodiments. Polarized light is suggested as a means of improving the contrast.

While the invention has been shown and described, particularly with reference to preferred embodiments thereof, and various alternatives have been suggested, it should be understood that those skilled in the art may effect still further changes without departing from the spirit and scope of the invention as defined hereinafter.

The invention claimed is:

1. The use of a resin film structure in a process for producing a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to van image to be recorded on a film structure of given optical characteristic comprising:

a smooth continuous obverse stratum of resin of relatively low melting point,

a reverse stratum, and

an intermediate stratum of material at least partially convertible, when heated with an electrostatic field applied thereto, to an optical characteristic of contrasting characteristic to be given optical characteristic of said film structure,

heating said film structure uniformly to a temperature sufficient to convert said intermediate stratum, thereby imparting an optical characteristic of contrasting nature to said film structure in those areas corresponding to the electrostatic charge pattern, and

cooling said film structure uniformly for solidifying the same.

2. The use of a film structure having a smooth dielectric surface in a process for producing a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to an image to be recorded on the dielectric surface of said film structure, said film structure having a supporting base and a layer carrying the dielectric surface selected from the group consisting of:

(1) a layer of a synthetic resin having a multitude of bubbles throughout the film structure, thereby giving the layer an opaque appearance,

(2) a layer of an organic compound selected from the group of crystalline waxes and crystalline resins, capable of changing from a crystalline state to an amorphous state upon heating,

(3) a layer consisting of a stratum of a fusible compound separating two stratum, each containing a -compound reactive with the other to form a colored product,

(4) a layer of continuous fusible compound having infusible particles dispersed therein, and

(5) a continuous fusible compound containing ferroelectric particles embedded in random orientation within said compound,

heating said film structure uniformly to a temperature such that the continuous component is in a thermally relaxed condition whereby, in the areas of said electrostatic charge pattern,

the cells of (l) collapse and render the areas transparent,

the crystalline component of (2) change into4 an amorphous state, p the two reactive components of (3) make contact and react,

the infusible parti-cles of (4) become exposed to the surface, and Y the ferroelectric particles of (5) reorientate in a uniform direction, and

Y cooling said film structure uniformly to solidify the film now having optically contrasting areas corresponding to said image. 3. The use of a resin film structure in a process for pro- 5 ducing a photographic record, including the steps of:

tov

establishing an electrostatic charge pattern corresponding to an image to be recorded on a film structure comprising,

a smooth 4continuous obverse stratum of said thermoplastic resin, and

a `stratum of said resin beneath said obverse stratum ducing a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to an image to be recorded on a film structure comprising,

a smooth continuous obverse stratum of crystalline wax or resin,

a stratum of said wax or resin of uniformly opaque characteristic in the crystalline state beneath said obverse stratum rendering said film structure opaque, and

a continuous base layer,

heating said film structure uniformly to a temperature sufficient to convert said wax or resin, where-by the crystalline wax or resin in the areas of said electrostatic charge pattern pass into the amorphous state, thereby rendering said film structure transparent in said areas,

`and

cooling said film structure uniformly for solidifying the same.

S. The use of -a resin film structure in a process for producing a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to an image to be recorded on a film structure comprising,

a smooth continuous obverse stratum of crystalline polyethylene,

Ia continuous base layer, and

a stratum of said crystalline polyethylene intermediate said obverse stratum and said base layer rendering `said film structure opaque,

heating said film structure uniformly to a temperature sufficient to convert said crystalline polyethylene, thereby transforming said crystalline polyethylene to the amorphous state in the areas of said electrostatic charge pattern, thereby rendering said film structure transparent in said areas,

and

cooling said film structure uniformly for solidifying the same.

6. The use of a resin film structure in a process for producing a photographic record, including the steps of:

heating said film structure uniformly to a temperature-sufficient to convert said crystalline resin, thereby 1 transforming said crystalline resin to the amorphous state in the areas of said electrostatic charge pattern, thereby rendering said film structure transparent in said' areas,

and

cooling Vsaid film structure uniformly for solidifying the same.

7. The use of a resin film structure in a process for producing a photographic record,` including the steps of: establishing Ian electrostatic charge pattern correspondproducing a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to an image to be recorded on a film structure compri-sing,

a continuous obverse stratum of thermoplastic resin,

a layer of resin containing encapsulated dyestuff imparting a uniform given color to said film structure, and

a layer of material containing a dye-former reactive with said dyestuff to impart color to said film structure contrasting with said given color,

heating said film structure uniformly to a temperature sufficient to convert at least said layer containing encapsulated dyestuff,

releasing said `dyestuff in the areas lcorresponding to said electrostatic charge pattern for effecting va reaction -of said Vdyestuff and said dye-former for producing an image of said contrasting color upon a background of said given color, and

cooling said film structure uniformly for solidifying rthe same.

9. The use of a resin film structure in a process for producing a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to an image to -be recorded on a film structure comprising,

a continuous obverse stratum of thermoplastic resin,

globules of dyestuff in said resin imparting a uniform field of given col-or `to said film structure, and

a continuous reverse stratum of material Icontaining a dye-former reactive with said dyestuf to impart color to said film structure contrasting with said given color,

heating said film structure uniformly to a temperature sufficient to convert said globules, thereby collapsing said globules in the areas corresponding to said electrostatic charge pattern for effecting a reaction of said dyestuff and said dye-former for producing an image of said contrasting color upon a background of said given color, and

cooling said film structure uniformly for solidifying the same.

10. The use of a resin film structure in a process for producing -a photographic record, including the steps of:

i establishing an electrostatic charge pattern corresponding to an image to be recorded on a film structure comprising, y a sheet of fusible resin and infusible particles embedded within said resin to leave a smooth, specular, reflecting, oblverse surface,

heating said film structure uniformly to a temperature sufficient to convert said fusible resin, thereby exposing said embedded particles in the areas where said electrostatic charge exists, and

cooling said film structure uniformly for solidifying the same, whereby 4 the exposed particles impart a roughened diffuse refiecting image surface against a specular reflecting background.

11. The use of a resin film structure in a process for producing a photographic record, including the steps of:

establishing an electrostatic charge pattern correspondying to an image to be recorded on a film structure comprising,

a sheet of fusible resin and particles embedded within said resin,

heating said film structure uniformly to a temperature sufficient to convert said fusible resin, thereby altering the position of said particles with respect to said sheet of resin in the areas 'where said electrostatic charge exists, and

cooling said film structure uniformly for solidifying the same, whereby the optical characteristic of said film structure differs in the charged areas from that in the uncharged areas.

12. The use of a resin film structure in a process for producing a photographic record, including the steps of:

establishing an electrostatic charge pattern vcorresponding to an image to be recorded on a film structure comprising, v

a plurality of strata of resin, including a continuous obverse stratum of vinyl resin of given color,

a succeeding stratum of fusible resin,

a following stratum of .material reactive with said vinyl resin for imparting a color contrasting with said given color, and

a reverse stratum of high melting point resin,

heating said -filmstructure uniformly to a temperature sufficient to convert said fusible resin, whereby said fusible resin flows away from the areas correspondling to said electrostatic charge pattern, and

cooling said film structure uniformly for solidifying the same, thereby forming a photographic record of an image of said contrasting color against a .background of said given color. Y

13. The use of a resin film structure in a processfor producing a photographic record, including the :steps of:

establishing an electrostatic charge pattern corresponding to a n image to be recorded on a film structure comprislng,

a plurality of strata of resin, including a continuous obverse stratum of vinyl acetate, substantially black,

`a succeeding stratum of fusible resin,

a following stratum of zinc-oxide, substantially white,

a reverse stratum of high melting point resin,

heating said film structure uniformly to a temperature sufiicient to convert said fusible resin, whereby -said fusible resin flows away from the areas corresponding to said electrostatic charge patterns, and

cooling said film structure uniformly for solidifying the same, thereby forming .a photographic record of a black image against a white background.

14. The use of a resin film structure in a process for producing a photographic record, including the steps of:

a fusible resin and elongated particles embedded in random orientation within said resin,

heating said lilm structure uniformly to a temperature sufficient to convert said resin for enabling reorientation of the particles therein, and

cooling said film structure uniformly for solid-ifying the same, Iand whereby said fusible resin melts uniform-ly in said heating step permitting said particles to change position in the areas Where said electrostatic charge exists, thereby altering the optical characteristics of said film structure in said areas.

15. The use of a resin iilm :structure in a process for producing 'a photographic record, including the steps of:

establishing an electrostatic charge pattern corresponding to an image to be recorded on a film structure comprising,

a fusible resin and elongated dielectric or ferroelectric crystalline particles embedded in random orientation Within said resin,

heating said film structure uniformly to a temperature :suicient to convert said resin for enabling reorientation of the particles therein, and

vcool-ing said lm structure uniformly for solidifying the same, and whereby said fusibile resin melts uniformly in said heating step permitting reorientation of said particles in uniform direction in the areas Where said electrostatic charge exists, thereby improving the optical transmission characteristic of said film structure in said areas as aga-inst the background areas of remaining randomly oriented particles.

16. The use of a resin film structure in a process for producing a photographic record, including the steps of:

establishing an' electrostatic charge pattern corresponding to an image to be recorded on a film structure comprising,

a layer of polyethylene Iand calcium citrate crystal particles embedded in random orientation Within said polyethylene,

heating said film structure uniformly to a temperture sufficient to convert said polyethylene for enabling rotation of said calcium citrate crystals the-rein,l

cooling said film structure uniformly for solidifying the same, `and whereby `said polyethylene melts uniformly in said heating step permitting reorientation of said crystals in uniform direction in the areas whe-re said electrostatic charge exists, thereby improving the optical transmission characteristic of said film structure in said areas as against the background areas of remaining randomly oriented crystals.

References Cited by the Examiner UNITED STATES PATENTS 2,584,441 2/1952 Fredendall 1l7-93.2 X 2,680,079 6/1954 Huebner ll793.2 3,079,253 '2/1963 Grieg 1l7-l7.5 3,206,755 9/1965 Friedman ..v 346-1 JOSEPH REBOLD, Primary Examiner.

W. L. JARvIs, Assistant Examiner. 

1. THE USE OF A RESIN FILM STRUCTURE IN A PROCESS FOR PRODUCING A PHOTOGRAPHIC RECORD, INCLUDING THE STEPS OF: ESTABLISHING AN ELECTROSTATIC CHARGE PATTERN CORRESPONDING TO AN IMAGE TO BE RECORDED ON A FILM STRUCTURE OF GIVEN OPTICAL CHARACTERISTICS COMPRISING: A SMOOTH CONTINUOUS OBSERVE STRATUM OF RESIN OF RELATIVELY LOW MELTING POINT, A REVERSE STRATUM, AND AN INTERMEDIATE STRATUM OF MATERIAL AT LEAST PARTIALLY CONVERTIBLE, WHEN HEATED WITH AN ELECTROSTATIC FIELD APPLIED THERETO, TO AN OPTICAL CHARACTERISTIC OF CONTRASTING CHARACTERISTIC TO BE GIVEN OPTICAL CHARACTERISTIC OF SAID FILM STRUCTURE, 